The present invention relates to an eyeglass lens processing apparatus that processes the peripheral edge of an eyeglass lens.
In processing apparatuses that process a peripheral edge of an eyeglass lens, the eyeglass lens is held by lens chuck shafts, a lens is rotated by the rotation of the lens chuck shafts, and the peripheral edge of the lens is roughed by pressing roughing tools, such as a rough grindstone, against the lens. When the lens chuck shafts are caused to hold the eyeglass lens, a cup that is a jig is fixed to a surface of the lens, the lens is mounted via the cup on a cup holder of one lens chuck shaft of the eyeglass lens processing apparatus, and the lens is chucked by a lens presser member of the other lens chuck shaft.
In recent years, water-repellant lenses with a water-repellant substance that neither water nor oil adheres easily is coated on the surface of the lens have often been used. Since the water-repellant lenses have a slippery surface, if the processing control is performed in the same manner as when processing lenses that are not coated with a water-repellant substance, a problem so-called “axis deviation”, that attachment of the cup may slip, and the rotation angle of the lens may deviate with respect to the rotation angle of the lens chuck shafts, is apt to occur.
As a method of reducing this “axis deviation”, the technique of detecting a load torque applied to the lens chuck shafts and reducing the lens rotating speed so that the load torque falls within a predetermined value is suggested (refer to JP-A-2004-255561). Additionally, as another method, there is suggested the technique of rotating a lens at a constant speed, and changing the axis-to-axis distance between the lens chuck shafts and a grindstone rotating shaft so that the amount being cut while the lens makes one rotation becomes substantially constant (refer to JP-A-2006-334701).